A medical mystery: Artificial hips that squeak

The first time John Johnson's artificial hip squeaked, he was bending down to pick up a pine cone in his yard in Thomasville, Georgia. Johnson looked up, expecting to find an animal nearby.

Susan O'Toole, a nutritionist at Montefiore Medical Center in New York, who first squeaked going up stairs after getting home from her hip replacement surgery in 2005, said she thought the banister she was gripping needed repair.

And Edward Heary, an apprentice appraiser in Hatboro, Pennsylvania, said clients sometimes look with embarrassment or concern at their floorboards when he walks though their homes.

As those three patients - and hundreds of others - discovered once they pinpointed the source of the noise, they had become guinea pigs in an unfolding medical mystery. Their artificial hips are made of ceramic materials that were promoted as being much more durable than older models. But for reasons not yet fully understood, their hips started to squeak, raising questions about whether the noises herald more serious malfunctions.

"There is something amiss here," said Dr. Douglas Padgett, chief of the Adult Reconstructive and Joint Replacement Service at Hospital for Special Surgery in New York. More than 250,000 Americans get total hip implants each year, a procedure that generally costs close to $45,000. Hip replacements have a success rate of more than 90 percent, based on patients' achieving relatively pain-free mobility after recovery periods that range from a few months to a year.

Any artificial hip can occasionally make a variety of noises. But until Stryker, a medical products company, began marketing highly durable ceramic hips in the United States in 2003, squeaking was rare.

Now, tens of thousands of ceramic hips later - from Stryker and other makers that entered the field - many patients say their squeaking hips are interfering with daily life. One study in The Journal of Arthroplasty found that 10 patients of 143 who received ceramic hips from 2003 to 2005, or 7 percent, developed squeaking.